The present invention pertains to forest products and particularly to the use of wood fibers.
Trees in the USA are of two general types for commercial purposes, hardwoods and softwoods. The softwoods are well utilized for the manufacture of newsprint, paper and the like paper products. Hardwoods, in the larger trees, are well utilized for the production of lumber.
However, the hardwood category also includes large numbers of relatively small trees, trees that are deformed or are otherwise not well shaped to produce commercial sizes and quantities of lumber, and the relatively larger as well as the smaller limbs of the larger hardwood trees which are not utilizable for lumber. The present invention is directed towards utilization of this resource.
That is, softwood production is well spoken for and most of the hardwood production is spoken for. It is the part of the hardwood production which is not otherwise usable at present which is usable in accordance with the invention to produce structural material such as panels with texturized surfaces and other objects of a particular category.
The prior art has been aware of certain problems in the use of hardwood fiber in methods such as the present invention that involve pressing of the fibers into products. Hardwoods tend to have short and thick walled fibers. These short thick walled fibers, when used in conventional processes of the same general category as the present invention and in paper making, tend to bond to each other only poorly, and, especially important as to paper, tend to exhibit poor tear strength and an abundance of natural and generated fine material that causes drainage problems resulting in low wet web strength. In the present state of the art, hardwood pulps are used primarily only as a filler and as a means to provide smoother surfaces on paper for printing.
Because of these problems, utilization of hardwoods of lower than lumber quality as set forth above has not occurred. This results in a good deal of waste of these lower quality hardwoods resulting in added pressure on softwood production.
In the prior art of the utilization of such wood fiber, the techniques utilized basically fall into two categories, using the fibers when they are wet, and using them when they are dry. The present invention is a dry or air as opposed to water deposition type of process.
The invention uses bonding techniques to form the final structural members. Wet techniques tend to be slower, involve many steps including those to drain the water used for the forming and to dry. These steps are all avoided with dry forming techniques such as the present invention.
Finally as to the prior art, attention is invited to two earlier patents, U.S. Pat. No. 4,702,870 issued Oct. 27, 1987 to Setterholm and Hunt; and U.S. Pat. No. 4,753,713 issued Jun. 28, 1988 to the present inventor, Dennis Gunderson. Both of these patents are owned by the U.S. Government, Secretary of Agriculture on behalf of the U.S. Forest Service.
Gunderson U.S. Pat. No. 4,753,713 teaches forming of a uniform density mat by draining a fiber bearing slurry through porous mandrels, and subsequent consolidation of the web in the mold. In U.S. Pat. No. 4,702,870, Setterholm and Hunt teach the wet-forming of a mat of variable cross-section on a support of resilient deformable mold inserts or "nubs" on a forming wire. They show how the web can be molded directly on the nubs and then consolidated as web and resilient inserts are pressed together under pressure applied normal to the surface of the web.
The present invention distinguishes from U.S. Pat. No. 4,753,713 in that: (1) the present invention is an air-forming and not a wet-forming method, (2) the present invention is not limited to drying on the mold, but provides means to remove the web from the mold and complete consolidation and cure thereof remote from the porous mandrels. The present invention distinguishes from Setterholm and Hunt in U.S. Pat. No. 4,702,870 in that the web is not formed on the resilient deformable blocks as taught by them--nor is it wet formed. Further, in the present invention, it is the protrusions in the forming apparatus which are porous whereas in Setterholm and Hunt it is the base material which is porous. In the present invention, there is significant one-dimensional (thickness direction) consolidation of the web on the mandrels. This is very significant because it permits the forming of much deeper sections (greater variations in cross-section) than is possible with the methods taught by Setterholm and Hunt. Moreover, the present invention teaches means to achieve further one-dimensional consolidation of the web even after the resilient pillows have been inserted in the web. The withdrawal of the solid block into the support plate (one-dimensional consolidation) prior to the distortion of the resilient pillows (three-dimensional consolidation) is not taught by Setterholm and Hunt.
A dry formed web cannot be adequately consolidated in the forming apparatus and the means to proceed with further consolidation and curing are not obvious from these prior patents. The present invention teaches a novel means to contain and support the web when the forming mandrel is withdrawn. Further, the invention teaches a novel means to proceed with consolidation of the web after it is removed from the mandrels.